WASHINGTON — Kentucky Senator Rand Paul is the first sitting Republican to come out against a potential cabinet member — and says he won’t support Ambassador John Bolton if Trump picks him for Secretary of State.

“I think an unrepentant advocate of the Iraq War doesn’t really fit with Donald Trump’s pronouncements throughout the campaign,” Paul told BuzzFeed News. “Donald Trump was quite proud of the fact that he opposed the Iraq War for a long time, and not only did he oppose it, he learned the lesson that regime change didn’t make America stronger or safer.”

Paul, who ran for president in 2016 on an anti-interventionist platform, said a potential Bolton appointment would be a “disaster” and contradictory to the positions Trump took on the campaign trail. Given the libertarian bent of other Republican members in the House and Senate, Paul said he expected others to join him in opposition.

Bolton has long been considered among the most hawkish personalities in Washington. He has advocated for regime change in Iran, opposing the Iran nuclear deal in favor of a military strikes and lobbying for the MEK opposition group. Bolton has also advocated that the US should threaten to, or actually, declare Taiwan independent as leverage against China.

“If you talk to Bolton or read his writings, he’s for regime change about everywhere you can imagine. He thinks the Iraq War was a great walk in the park, and great for the country and it was an unmitigated disaster. He would have regime change in Iran, he would bomb Iran,” Paul said. “I think he said it every six months, or every couple months for the last decade.”

Bolton served for one-year as US ambassador to the United Nations as a recess appointment under President George W Bush. He was unable to receive a confirmation under either a Republican or Democrat-controlled Senate, leading him to leave the government in 2007.

The other name that has been floated as a top candidate for Secretary of State is former New York mayor Rudy Giuliani, a Trump loyalist who was mayor during 9/11 but has no foreign policy experience. To Paul, Giuliani’s positions on Iran and support of Middle East intervention are also a cause for concern.

“In this instance, particularly in Giuliani's case maybe there would be less of a problem if he were appointed to a position where he didn’t directly contradict what Trump advocated,” he said. “There’s a way to reward loyalty basically without sending mixed signals on what your foreign policy will be.”

Paul said he’s hopeful that someone like Sen. Bob Corker, the chairman of the Senate Foreign Relations Committee will ultimately get the Secretary of State job, though Corker is reportedly out of the running for the position.

“He and I don’t agree on everything but he’s a vastly better choice than a guy who wants to bomb every chance he gets.”

Kate Nocera is the managing editor for BuzzFeed’s Washington, DC bureau. Nocera is a recipient of the National Press Foundation's 2014 Dirksen Award for distinguished reporting on Congress.